Three methods to reduce the RCS of Fabry-Perot (FP) resonator antenna using diffuse scattering are verified and compared in this paper. They are 1 bit random coding, 2 bit random coding, and 2 bit random phase gradient coding method. In order to realize reflection phase coding, a receiver-transmitter type unit with adjustable reflection phase from top side is proposed. Metasurface (MS) composed of this unit is the best choice to achieve the RCS reduction of FP resonator antenna, because it has the ability to independently control the reflection phase on both sides. By changing the size of radiation patch, two units with 90° reflection phase difference and four units with 90° reflection phase difference from top side can be obtained. They are used to compose MSs with different reflection phase distributions. These MSs can form FP resonator antennas with RCS reduction characteristics. Subsequently, three antennas are fabricated and tested, and the test results are compared. The results show that the FP resonator antenna using 2-bit random phase gradient coding has the best performance. It achieves the wideband RCS reduction of antenna and has the least influence on radiation performance. The proposed antenna A3 achieves an average RCS reduction of 12 dB over the bandwidth range of 7.7-13.7 GHz while maintaining a peak gain of 18 dB and good radiation patterns.

This paper introduces a novel RF phase shifter design that operates at constant phase shift over operation frequency range. The proposed phase shifter utilizes the conventional reflective-type phase shifter which is inherently frequency-dependent. The introduced reflective-type phase shifter design is integrated with an adaptive control circuit that varies the required DC voltage as a function of the frequency. Thus, the phase shift will be relatively constant throughout the frequency of operation compared to the conventional frequency-dependent reflective-type phase shifter. The phase shifter is designed to operate at 90˚ and is shown to maintain that phase shift with around 15˚ compared to the conventional design where the phase shift varies by more than 60˚ at the same bandwidth. The proposed design, including the adaptive controlled circuit, is fabricated, and the measured data agree with simulations.

A screen-printed wearable coplanar waveguide (CPW) fed semi-octagonal shaped antenna is developed on a denim textile substrate to resonate at 2.45 GHz for wireless medical body area network communications. The antenna is integrated with a circular ring-type electromagnetic bandgap structure (EBG) to mitigate performance degradation due to the high permittivity of the tissue model when it works on body conditions. The CPW antenna and EBG surfaces are fabricated using the screen-printing method, which provides good conformability, good wearable comfortability, and light weight. The proposed EBG integrated antenna has dimensions of 0.66λ × 0.66λ × 0.056λ and an impedance bandwidth of 13% (2.3-2.62 GHz) with a gain of 6.7 dB. The specific absorption rates (SARs) of the antenna are 0.309 W/kg and 0.14 W/kg for 1 g and 10 g of tissue, respectively, which are within the wearable safety limits. Thus, the fabricated prototype antenna is suitable for wearable WBAN and MBAN applications.

A new tri band rectangular DRA is simulated and tested for wireless communication applications like ISM, Wi-Max, and WLAN. The dielectric resonator antenna structure is excited by a 50 Ω transmission line. The rectangular DRA with concentric square rings is designed to acquire the operation of triple-bands. The parametric analysis of the rectangular DRA has been carried on HFSS tool. The rectangular DRA exhibits triple-band characteristics at 2.16-2.57 GHz, 3.35-4.45 GHz, and 5.35-5.95 GHz, with a fractional bandwidth of 17.3%, 28.1%, and 10.6%, respectively. The implemented concentric square rings are imposed on FR4-substrate material to emphasize the antenna parameters and to minimize the size. The designed DRA has a compact size, good radiation properties and optimal operational bandwidth. To validate the antenna, it is fabricated, and the fabricated DRA results match well with the simulated ones. The antenna is well suitable for wireless communication applications. The fabricated rectangular DRA is measured by using MS2037C Anritsu-Combinational Analyzer.

In this article, a novel transmission line (TL) based on coplanar waveguide (CPW) spoof surface plasmon polariton (SSPP) with flipper structures is proposed to improve field confinement. An equivalent circuit (E.C) is developed to analyze the proposed SSPP. The E.C analyses reveals that the proposed unit exhibits flexibly controllable dispersion features and improved field confinements owing to the introduction of the flipper structures. Finally, the proposed SSPP TL is designed, fabricated, and tested to validate the design principles. The experiment results illustrate the theoretical analyses and validate that the proposed SSPP TL exhibits ultra-compact size occupation and enhanced field confinement.

Absorbing materials can absorb incident electromagnetic waves effectively and have important research value in radar fields. However, the current absorbing materials are mostly affected by the thickness and flexibility of the dielectric substrate, and they have shortcomings such as being not thin, not flexible, not folding, and not conformal with the protection target, which is not conducive to practical application. In this paper, we propose a flexible absorbing material that can be folded freely for wearable and practical engineering applications, which is composed of a conductive carbon paste ink resistance film layer, a flexible fabric dielectric substrate and a metal backplane. When the incidence angle is less than 30°, more than 90% absorption performance can be achieved at the operating frequency of 9.5-11.5 GHz with polarization insensitive characteristics. Simulated and experimental results prove the effectiveness of the structure. Our work provides the groundwork for the commercialization of future meta-devices such as wearable invisibility cloaks, sensors, optical filters/switchers, photodetectors, and energy converters.

In this paper, an ultrawideband linear cross polarization converter based on metasurface (MS) with wide incidence angle is presented and applied to the reduction of radarcross section (RCS) for planar and conformal surfaces. A pair of bow-and-arrow shaped split ring cells is printed onan FR4 dielectric substrate. The simulated and experimental results indicate that the converter achieves a cross polarization conversion ratio (PCR) of over 90% in 11.5-28.5 GHz (85% relative bandwidth), and that its oblique incidence performance can be stabilized at ±40° with a very small loss of bandwidth (1.65%). Then, the polarization conversion metasurface (PCM) cells and their mirror cells are laid out in a checkerboard array and applied to reduce RCS of planar and conformal surfaces. The planar PCM achieves more than 7 dB of RCS reduction in 11.4 to 29.6 GHz (88.8% relative bandwidth), and the conformal array with a center angle of 90°obtains more than 10 dB RCS reduction in 18.2 to 23.7 GHz. Due to its excellent performances, the proposed metasurface offers promising options for polarization control devices and stealth technology in Ku- and K-bands.

A metasurface that can be reconfigured for the conversion of linear-to-linear polarization has been designed, fabricated, and verified. It consists of dual co-centric split-ring resonators (SRRs), each of which has a pair of splits. It is specifically engineered to function in two reflection modes, one with polarization conversion and the other without. The unit cell achieves reconfiguration by utilizing two PIN diodes. Conversion of linear polarization to its perpendicular counterpart is achieved while the diodes are in OFF state. When the PIN diodes are turned on, full reflection without polarization conversion occurs. The proposed meta-surface operates over the 6.03-10.5 GHz frequency range. A 42×42 unit cell array is fabricated, and the results are experimentally verified. An FR4 substrate is used with copper ground plane on one side. The polarization conversion is measured and compared to simulation results for various incident angles. A Polarization Conversion Ratio (PCR) of ≥90% is achieved for incident angles up to 30°, with simulation and measured results showing good agreement.

This letter presents a wideband multi-linear polarization reconfigurable antenna, which has the ability to switch among four linear polarizations at rotation angle of 45°, namely 0°, 45°, 90° and -45°. Its main structure consists of three layers of substrates and a reflective cavity. Four pairs of crossed bow-tie dipoles are used as the primary radiators, and the polarization switching is realized by controlling the ON/OFF states of four pairs of PIN diodes between feeding source and the dipoles. In addition, circular ring and reflective cavity structures are used for enhancing the operating bandwidth, stabilizing the radiation patterns and increasing the gain. Finally, the simulation and measurement results both demonstrate that the antenna exhibits an overlapped impedance bandwidth of 42.6% (2.4 GHz-3.7 GHz) for all polarization states, and it remains a steady radiation pattern within the operating bandwidth. With these features, the design can be used in wireless communication systems in the 5G sub-6 GHz band.

This paper presents a circularly polarized double wall substrate integrated waveguide (SIW) fractal slot antenna array designed for X-band satellite applications. The proposed antenna demonstrates a reflection coefficient, covering the frequency range from 7.3 GHz to 8.5 GHz. The antenna is circularly polarized with a 3-dB axial ratio bandwidth ranging from 7.88 GHz to 8.58 GHz. The antenna array exhibits a gain variation between 11 dBi and 12.51 dBi. Moreover, the proposed design achieves an efficiency of 89%. With overall dimensions of 177 mm x 48.8 mm x 3.175 mm (4.8λ₀ x 1.32λ₀ x 0.086λ₀), the antenna array is compact and suitable for satellites with limited surface area. This compact form factor facilitates seamless integration into satellite systems without compromising performance. The proposed antenna is suitable to be employed for the satellite X-band telemetry application extending from 7.9 GHz to 8.4 GHz. A prototype of the proposed antenna has been fabricated and then measured using Vector Network Analyzer (VNA) and Anechoic chamber. The proposed antenna's measurement results match the simulated results.

This study aims to achieve the co-optimization of thrust force and thrust fluctuation using a long secondary double-sided linear flux switching permanent magnet motor (LSDLFSPM). Firstly, the motor model is constructed and derived using a theoretical approach. Subsequently, the motor parameters are subjected to sensitivity analysis using the Taguchi method to identify the significant influencing factors. Based on the screening results, the Response Surface Method (RSM) is employed to construct the test space and derive regression equations for thrust force and thrust fluctuation. The Multi-Objective Grasshopper Optimization Algorithm (MOGOA) is then utilized to iteratively optimize the regression equation for optimal parameter sizes. Finally, the optimized results are validated through finite element analysis (FEA) and compared with the original motor performance to demonstrate the effectiveness of the optimization approach proposed in this paper.

To reduce the coupling between closely packed antenna elements in multiple-input multiple-output (MIMO) systems, a method is proposed to reduce the coupling between planar inverted F-shaped antennas (PIFAs) by using cross slot defected ground structure (CSDGS). This structure includes four intersecting slits etched into the ground plane. The resonant frequency of the PIFA is within the bandgap of the CSDGS, effectively suppressing surface waves and reducing the coupling between antennas. Through simulation, it is demonstrated that the proposed structure achieves more than 35 dB isolation between two antenna elements. To validate the effectiveness of the method, the circuit of the simulated structure is processed and measured using a vector network analyzer. The measured results align closely with the simulated ones, confirming the viability of the proposed method. The parameter study and correlation coefficient of CSDGS are also analyzed.

Recently, clustered antenna arrays have been proved as an efficient method in implementing the large planar arrays for massive MIMO wireless communications in 5G and beyond applications. However, obtaining optimum clustering configurations needs a high computational time, and it does not guarantee a total clustering coverage of the whole array aperture. In this paper, a new and unconventional array pattern synthesis method based on ascending/descending clustered subarray rings is presented. The method is equally applicable to the rectangular and circular planar arrays where they are first divided into multiple square or circular clustered rings starting from the largest ring at the array perimeter up to the last ring (the smallest one) at the array center. Then the amplitude distributions of these clustered rings are optimized to obtain the desired radiation characteristics subject to the user-defined constraint mask. Implementation of the proposed array at the clustered level instead of the conventional element level offers many advantages such as simplified feeding network, efficient taper efficiency, low sidelobe level, and high directivity. Simulation results show the effectiveness of the proposed method for both square and circular planar array layouts.

Based on a framework recently published, the double-Cornu spiral antenna is extended to an array to enhance the gain. The designed array of 2×2-elements is of low profile and small sizes, has however a large effective bandwidth, and shows overall good radiation characteristics: enhanced gain, large axial ratio bandwidth, and high degree of polarization purity. Except for a few deviations, which are due to manufacturing tolerances, artificial noise and measurement uncertainties on the one hand and diffracted waves at external edges on the other, simulated results and experimental data fit well together. In addition, EMC along with signal integrity issues related to the reduction of noise and unwanted radiation have been addressed. The proposed antenna is suitable for 5G applications and radar systems. With 14.02 dB realized gain, 6.2 GHz effective bandwidth and an uplink data rate of 3.44 Mbit/s, the array is promising for many mobility applications.

We have developed a fast method of using Multiple Scattering Theory-Broadband Green's Function (MST-BBGF) for band field calculations. In this paper, we successfully extended the method to the vector electromagnetic case of 3D periodic structures. In the MST-BBGF approach, the broadband transformation to vector spherical waves for 3D is derived using the Broadband Green's function. The band eigenvalue problem is expressed in terms of the single scatterer T matrix which is independent of the periodic lattice nor the Bloch vector. For the first five bands, the dimension of the KKR eigen equation is merely 6, as 6 vector spherical waves are utilized for the scattered waves. We make extensive comparisons of the results with the commercial software COMSOL in both accuracy and computation efficiency. The CPU requirementon a standard laptop for the MST-BBGF method is merely 0.309 seconds for the first 5 bands. The MST-BBGF method is accurate and is at least two orders of magnitude faster than commercial software COMSOL. In the band field calculations, we employ the approach of extended coefficient to use the low order eigenvector of 6 to extend to 240 vector spherical wave coefficients without the need of re-calculating the eigenvalue nor the eigenvector of the KKR equation. The extended coefficients approach gives accurate band field solutions for the entire (0,0,0) cell.

The fusion of electromagnetic (EM) waves and information theory in wireless and waveguide communication technologies has enjoyed a remarkable revival during the last few years. In particular, unlike traditional transceiver systems, the recently proposed information metasurface system directly links the controllable binary array sources with the scattered EM waves, making the combination of EM and information theories highly desirable and natural. Moreover, a traditional linear channel matrix cannot be directly used for such scattering reconfigurability enabled communication system, making the information characterization of such system a great challenge. In this paper, EM information characteristics of a direct digital modulation (DDM) system enabled by programmable information metasurface, also known as reconfigurable intelligent surface (RIS), are analyzed, in which RIS is used as a modulator of the illuminating field, while the scattered far-field amplitudes are measured and effectively treated as the received quantities. The posterior probability for a specific source coding pattern, conditioned over a given measured scattering fields, is obtained through the Bayesian analysis technique, from which the average mutual information (AMI) is obtained to estimate the RIS observation capability along any particular direction. The averaged receiver mutual information (ARMI) is then introduced to characterize the generated field correlation structures along different observation directions. Based on ARMI, the joint observation capability is also analyzed. Furthermore, the suggested techniques are employed in a noisy environment, and a code selection scheme is put forth to achieve efficient information transmission. The proposed configuration is validated through a simulated experiment. As a comprehensive evaluation of the system's performance, the channel capacity of the system is derived, and a set of relevant influencing factors are identified and analyzed from four different perspectives: 1) the observation direction, 2) the size of RIS, 3) potential joint observations in multiple directions, and 4) the noise level. The proposed method, together with the various related performance measure metrics introduced therein, are expected to provide the research community with guidelines for analyzing and designing the current and future RIS-based communication systems, which can also be extended to other aspects in the growing field of the EM information theory.

The introduction of microfluidics technology with graphene provides many advantages, such as improving the selectivity and sensitivity, achieving chemical and thermal stability, decreasing the size of devices, and impoving the cell and The biological response of the substance. The principal objective of this paper is to compare the constitutive parameters in order to develop graphene-based microfluidic sensors. The simulation results illustrate that the suggested sensor exhibits a strong ability in detecting normal skin tissue with an exellent sensitivity of 6.060 (THz/RIU) and to identify skin cancer with a notably significant sensitivity of 4.59 THz/RIU. Additionally, it shows considerable figure of merits, with values of 550.9 and 353.61 RIU, respectively. In conclusion, the simplicity, effectiveness, and adjustability of the proposed biosensor render it well-suited for breast tumor detection.

In electrical machines, most of the iron loss estimation in finite element modeling is based on Bertotti coefficients obtained from the corresponding data sheet. However, often a more exact estimation of coefficients for the laminated steel material is needed. Especially in the case of high speed machines (where iron loss has the highest contribution to the total loss), it is very difficult to estimate the iron loss variation as a result of laser cutting when just using data sheet information as input data in finite element analysis. Laser cutting impacts also the magnetic properties, in terms of magnetization curves at different frequencies, not only the core losses. In this paper, three different core materials of the same lamination steel are prepared to realize the estimation of the Berttotti loss coefficient when the material is subjected to high frequency and under the stress of laser cutting. Experimental analysis is performed to obtain more precise values of Bertotti coefficients at a high frequency range so that they can be utilized in iron loss estimation in a high speed machine (100 krpm maximum speed-1667 Hz) which is further shown as an application. Finally, it is shown how frequency domain iron loss results can be utilized for the time stepping iron loss analysis.

In this paper, a comparison microwave method between Transmission and Reflection using a Coaxial Cable and complimentary double split ring resonator (CDSRR) for characterization of magneto-dielectric material is proposed. This method enables the determination of both relative permittivity and permeability of magneto-dielectric material. The CDSRR resonates at 3.46 GHz with a quality factor of 127 in unloaded condition. To determine the effects of permittivity and permeability on the shift of resonant frequency, the electric and magnetic fields are localized in two separate zones in the CDSRR sensor. Prediction formulas are proposed to extract the value of real permittivity and permeability from S₂₁ parameter. For Transmission/Reflection Method, to extract the dielectric and magnetic properties, Nicolson-Ross-Weir (NRW) are used. The prototypes of proposed sensors are fabricated on a ROGERS 3003 and tested for validation of their functionality. A good agreement between the measured data using Transmission/Reflection Method and CDSRR sensor is observed.

For applications involving triple bands, a small slot structure loaded with an asymmetric split ring resonator (ASRR) is suggested in this article. The slot mode, which is agitated with the help of a microstrip line feed, produces the first band. 2.24 GHz resonance frequency is the intended operating band. The sand third frequency bands are achieved by loading ASRR on the slot. The slot produces axial magnetic field required to excite the ASRR. The asymmetry introduced in the conventional SRR produces dual resonances. The ASRR gives the resonant frequencies at 2.97 GHz and 3.66 GHz. The frequency bands of the slot and ASRR can be independently tuned. The proposed geometry is verified experimentally, and it is in good agreement with the simulated one. The impedance bandwidth of all three resonant bands measured from experiment are 14.25%, 1.78%, 8.37%. The peak gains of 3.1 dBi, 2.18 dBi, and 3.29 dBi are obtained at resonant points, respectively. The designed antenna is compact and well suits for wireless application like WLAN, GPS, and LTE48/TD3600.